The present invention relates to fluid-powered rotary motion actuating devices and particularly to such devices of the dual-piston type.
Actuators of the relevant type above-indicated characteristically have an annular housing or body containing a pair of pistons interconnected by gearing, such as a rack-and-pinion mechanism, or a like arrangement for controlling opposed reciprocal movements of the pistons toward and away from one another under operating fluid pressure while producing rotary reciprocation of the piston interconnecting arrangement to provide a desired rotary motion output therefrom. Various types of such actuators designed for both pneumatic and hydraulic operation and utilized in diverse embodiments and for differing purposes are well known. Representative examples of such actuators are disclosed in U.S. Pat. Nos. 1,667,559; 2,811,148; 2,849,888; 3,971,296; 3,982,725; 4,167,897; 4,203,351; and 4,354,424. Other representative examples of such actuators are the "WATTS RPD" and "WATTS RPS" Series double rack-and-pinion pneumatic actuators, manufactured by Watts Regulator Company, of Lawrence, Massachusetts; the "DYNAMATE F-790" pneumatic rotary actuator, manufactured by Keystone Valve USA Division of Keystone International, Inc., of Houston, Texas; the "EL-O-MATIC" pneumatic rotary actuator, which is of the basic type of the aforementioned U.S. Pat. No. 4,203,351, and is manufactured by Humabo Machinefabriek B. V., of Hengelo, Netherlands; and the "SHAFER HYTORK" pneumatic actuator, manufactured by Shafer-Hytork, of Mansfield, Ohio.
These actuators are basically operated by directing a pressurized fluid into an intermediate chamber of the housing defined between the two pistons while exhausting pressurized fluid from the chambers within the housing axially outwardly of the pistons to force the pistons away from one another and to rotate the interconnecting arrangement in one direction, and are alternately operated by directing pressurized fluid into the axially outward chambers while exhausting pressurized fluid from the intermediate chamber to force the pistons toward one another and to rotate the interconnecting arrangement in the opposite direction.
One of the engineering problems and restrictions in designing such actuators is the need to provide appropriate fluid passageways for conveying the pressurized operating to and from the fluid chambers of the actuator. Typically, this necessity is accomplished by fabricating the housing as a relatively thick-walled unitarily-cast annular metal housing to facilitate the formation of appropriate fluid passageways through the annular housing or, alternatively, relatively complex systems of tubular conduits may be arranged exteriorly of the housing for delivering fluid to and exhausting fluid from the interior chambers. In each case, the relatively complex resultant design requires correspondingly expensive fabrication and assembly of the actuator. Furthermore, with actuators of the type utilizing a cast metal housing, the necessary casting process limits the available materials from which the actuator housing can be fabricated and results in a relatively heavier and less compact actuator. On the other hand, actuators employing an exterior conduit network are similarly less compact and additionally are highly subject to breakage and damage of the fluid tubing.
In contrast, the present invention provides an actuator of the dual piston type having an improved fluid conveying system which requires neither complex porting and passageways in the actuator housing or an exterior piping or tubing system, and furthermore advantageously facilitates a simple and easy fabrication with a radically different piece parts design and using heretofore uncoventional materials.